Means to decelerate a towline reel



April 16, 1963 D. M. JONES 3,085,769

MEANS TO DECELERATE A TOWLINE REEL Filed Dec. 7, 1959 5 Sheets-Sheet 1 .j I4 j. 'L Il 4 April 16, 1963 D. M. JONES MEANS To DECELERATE A TowLINE REEL 3 Sheets-Sheet 2 Filed Dec. 7, 1959 April 16, 1963 D. M. JONES 3,085,769

MEANS 'ro DECELERATE A TOWLINE REEL Filed Dec. '7, 1959 3 Sheets-Sheet 3 United tates This invention relates to means to decelerate a reel to terminate the reeling in of an object on the end of the towline.

The practices of the invention selected for the present disclosure relate to an apparatus on an aircraft for retrieving a streamlined tow target on the end of a towline that is many thousands of feet in length. To retrieve the tow target after a target exercise, a variable speed power-actuated reel on the aircraft winds in the towline to bring the tow target eventually into contact with a launcher on the aircraft, which launcher is retractable against the force of a launcher spring. After the tow target makes contact with the launcher, the reeling operation is continued to retract the launcher cornpletely. The reel may be driven in a variable manner, for example, by means of an air screw of the general construction of a variable pitch propeller, the rate at which the reel is driven being varied by varying the pitch of the blades of the air screw.

In the retraction of the launcher, the launcher spring absorbs energy to decelerate the rapidly moving tow target, the tow target being brought to a stop within a range on the order of thirty inches. The present invention is directed to the problem of decelerating the rotating reel within the time interval in which the launcher is retracted by the tow target. This time interval varies inversely with the velocity of the tow target at the moment of initial contact of the tow target with the launcher. The required braking force rises lrapidly with rise in velocity of the tow target not only because the deceleration must be completed in shorter time but also because the energy to be dissipated increases with the square of the angular velocity of the reel, The problem, then, is first to initiate the braking operation when the tow target reaches the launcher and second to apply the correct magnitude of braking force for stopping the reel as the launcher reaches complete retraction.

The invention meets this problem by employing a brake that is adjustable with respect to its braking force, by providing means to detect the speed of rotation of -the reel, and by providing means to initiate the braking action in response to arrival of the tow target at the launcher with the braking force adjusted in accord with the detected speed.

In the simplest practice of the invention, the brake is manually adjustable with respect to its braking force and a tachometer operatively connected with the reel affords guidance for the operator in the manual adjustment of the brake. A feature of this practice of the invention is the concept of calibrating the brake adjustment in terms of the tachometer scale.

In a second practice of -the invention, the adjustment of the brake is carried out automatically. For this purpose, a tachometer generator may be connected to the input of an amplifier that determines the amount of braking force applied by the brake. Thus the tachometer generator senses the rotation of the reel and accordingly governs the braking force that is applied when the brake is operated in response to arrival of the tow target at the launcher. The gain characteristics of the amplier may be such as to vary the braking force in any desired manner.

In a modified practice of the invention, the amplifier is operatively connected to a function generator which in turn governs the braking force. For example, the amplifier may control the movement of a sliding contact along a card potentiometer which controls the amount of current supplied to an electric brake.

The features and advantages Iof the invention may be understood from the following detailed description together with the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative FIG. l is a simplified elevational View of an installa- -tion on an aircraft for controlling a tow target, Ithe installation including a reel, a brake and a tow target launcher, the tow target being shown spaced from the launcher;

FIG. 2 is a fragmentary view similar to FIG. l showing the tow target snubbed to the retracted launcher;

FIG. 3 is an enlarged fragmentary sectional view showing how a switch may be incorporatedin the launcher construction to initiate the operation of the brake;

FIG. 4 is a face View of an auxiliary panel on which is mounted both a potentiometer for adjusting the braking force and an override switch for the brake circuit;

FIG. 5 is a longitudinal sectional View of the launcher in its extended state ready to receive a tow target;

FIG. 6 is a similar view of the launcher in its latched retractedV state with the tow target locked therein;

FIG. 7 is a wiring diagram illustrating the simplest practice of the invention in which the brake is manually adjusted in accord with the observed speed of rotation of the reel;

FIG. 8 is a wiring diagram of an automatic arrangement in which a tachometer generator and an amplifier are employed to adjust the braking force automatically in accord with the speed of rotation of the reel; and

FIG. 9 is a diagram illustrating the manner in which the amplifier may control a function generator which in turn controls the brake. v

FIG. l shows diagrammatically a tow target installation for an aircraft which includes a streamlined tow target 10 on a towline 12, a launcher, generally designated L, for the tow target and a reeling unit R for controlling the towline. The reeling unit R is mounted on the underside of a towing aircraft 14 by means of a pylon 15 and the launcher L may be mounted on the aircraft in a similar manner by a second pylon 16 at a few feet from the reeling unit. The towline 12 is wound on a reel 18 in the reeling unit and extends from the reeling unit to the launcher L and through the launcher to the tow target 10.

The reeling unit R may be of the general construction of the reeling unit disclosed in the Hopper et al. patent, No. 2,751,167, dated June 19, 1956, and the launcher L may be of the general construction disclosed in the Hopper patent, No. 2,813,719, issued November 19, 1957, or of the general rconstruction disclosed in the allowed copending Hopper et al. application, Serial No. 575,015. These three -prior art disclosures are hereby incorporated in the present disclosure by reference.

The reeling unit R inculdes an air screw 20 of the general character of a variable pitch` propeller for driving the reel 18 at various rates of speed. 'The air screw 20 is operatively connected lto the reel 18 by means of a drive shaft 22 that extends through a brake 24, the purpose of the brake being to decelerate or immobilize the reel 18 when desired. The brake 24 may be an electrically actuated magnetic brake, such as lthe model PB 500 brake manufactured by Warner Electric Brake and Clutch Company, Beloit, Wisconsin. The reeling unit R is remotely controlled from a control panel 2,5 inside the towing aircraft, the reeling unit being connected with the panel through a multiple conductor cable 26.

The laun-cher L may be of the specific construction shown in FIGS. 5 and 6 and the nose of the tow target may be of the construction shown in FIG. -1 for cooperation with this launcher. As shown in FIG. 1, the tow target 410 has a tapered nose 28 with a swivel member mounted thereon for attaching the towline 12 to the tow target. The swivel member has a conical body 30 mounted on an axial stem 32, which conical body forms a rearwardly directed shoulder for engagement by suitable latching means, as will be explained.

As shown in FIGS. and 6, the launcher L has a cylindrical housing 34 in which a launcher tube 35 is mounted in a retractable manner. In the construction shown, the launcher tube is movably mounted in a pair of spaced ball bushings 36 which in turn are mounted in an inner cylinder 38. The inner cylinder is anchored at its forward end in a reinforcing ring 40 inside the cylindrical housing 34 and at its rear end is mounted in a cylindrical casting 42 at the aft end of the housing 34.

The inner end of the launcher tube 35 carries a circular casting 44 which backs against the forward end of a coiled launcher spring 45. A latching lug 46 extending radially from the casting 42 through a longitudinal slot 48 in the cylindrical housing 34 is positioned to cooperate with a spring-pressed latching pawl 5t) that may be retracted by a solenoid 52. When the launching tube 35 is completely retracted by reeling in the tow target 10, the latching lug moves against an inclined face of the latching pawl 50 to retract `the latching pawl yand then is automatically engaged by the latching pawl to be held in it-s retracted position. i

The outer end of the launching tube 35 carries a conical seat 54 for the conical body 30 of the swivel fitting of the tow target and this conical seat is provided with a plurality of latching dogs 55 to engage the shoulder of the conical body. The latching dogs 55 are triangular members pivotally mounted in pairs of ears and are rotatable in corresponding slots in the wall of the conical seat 54. Suitable torque springs (not shown) are provided to urge the latching dogs to their release positions shown in FIG. 5.

When the launcher tube 35 is retracted longitudinally against the launcher spring 45, the latching dogs 55 encounter the cylindrical casting 42 and are thereby rotated to their effective positions shown in FIG. `6 at which they engage the conical body 30 of the swivel fitting to lock the snubbed tow target in the retracted launcher. Since the latching pawl 50 holds the launcher tube 35 in its retracted position, and since the latching dogs 55 are then at their effective positions, it is apparent that the latching pawl also serves indirectly to lock the tow target to the retracted launcher. When the tow target is locked to the retracted launcher in this manner, a basket-like frame embraces the nose of the tow target to stabilize the tow target in Ithe launcher. As shown in FIGS. 1 and 2, the basket-like frame comprises a ring member 58 to embrace the tow target and a plurality of divergent frame members 60 braced by struts 62.

The towline 12 extends from the reeling unit R through the air to the pylon 16 and then is routed by guide pulleys 64 and 65 to the forward end of the launcher. From the guide pulley 65, the towline extends along the axis of the launcher through the launcher spring 45, the launcher tube 35 and lche conical seat 54 to the tow target.

When the towing aircraft is on the ground in preparation for transporting the tow target to a target practice area, the tow target is snubbed to the retracted launcher L in the manner shown in FIG. 2 with the latching dogs 55 eifective to hold the tow target seated in the launcher and with the latching pawl 50 effective to hold the launcher in its retracted state. rWhen the target practice area is reached, the operator on the towing aircraft releases the brake 24 and energizes the solenoid 52 to retract the latching pawl 50, whereupon the launcher spring 45 forcibly extends the launcher tube 35 to thrust the tow target into the air. As the conical seat 54 of the launcher clears the circular casting 42, the latching dogs 55 rotate l to their release positions to free the tow target from the launcher. The tow target is then reeled out. The unwinding rotation of the reel may be controlled by varying the pitch of the air screw 20 and by energizing the brake 24, if necessary. f

When the time arrives for retrieving the tow target 10 at the end of a target practice, the air screw 20 is ernployed to rotate the reel 18 at a suitable speed for winding in the towline. When the conical body 30 of the swivel fitting enters the conical seat 54 of the launcher, the continued reeling in of the cable causes the tow target to retract the launcher tube 35 until the tube is engaged by the latching pawl 50. In the course of the retraction of the tube 35, the latching dogs 55. are rotated to their effective positions to lock the tow target to the launcher, as heretofore described.

As heretofore stated, the problem to which the present invention is directed is to control the brake 24 for deenergizing the rotating reel 18 to bring the reel to substantially a stop or close to a stop as the launcher tube 35 reaches its retracted latched position. In all practices of the invention, a suitable switch is provided to operate the brake 24 in response to the arrival of the tow target 10 at the conical seat 54. Such a switch may be provided in the manner shown in FIG. 3.

In FIG. 3, a normally closed switch 66 is positioned inside the cylindrical launcher housing 34 on the previously mentioned reinforcing ring 40. The switch has an operating plunger 68 that extends through the reinforcing ring 40 in a position to be depressed by the circular casting 44 on the inner end of the launcher tube 35 when the launcher tube is at its extended position. When the launcher tube 35 is initially retracted from. its fully extended position, the operating plunger 68 is released by the casting 44- to permit the switch 66 to close for energization of the brake 24.

In the first practice of the invention, the brake 24 is controlled by the circuit shown in FIG. 7. In FIG. 7, the brake 24 is energized by two leads 70 and 72 from a suitable 28-volt source. The lead 70 is connected to the brake 24 through a fixed resistor 74 and a variable resistor or potentiometer 75, the two resistors being in series. The previously mentioned switch 66 is in series with a second override switch 76, the two Switches being in series. When the `switch 66 is closed in response to the arrival of the tow target at the launcher L, the brake 24 is automatically energized and the brake exerts a brak- Iing force which depends upon the manual adjustment of the potentiometer 75.

The operator may use his judgment based on experience in adjusting the potentiometer 75 but a feature of this practice of the invention is the provision of a tachometer actuated by the reel 18 to afford guidance in the manual setting of the potentiometer 75. Such a tachometer, designated by numeral 78, is provided on the previously mentioned control panel 25 and is shown in phantom in FIG. 4.

A feature of this practice of the invention is the further concept of providing a potentiometer 75 which is calibrated in terms of the scale of the tachometer 78. For this purpose, the potentiometer 75 may be mounted on an auxiliary control panel on a cable S2 that branches from the previously mentioned cable 26. As best shown in FIG. 4, the potentiometer 75 is represented by a manually adjustable rotary pointer which traverses a circular scale having numerals representing different r.p.m. values shown on the tachometer 78. The override switch 76 is also on the panel 80 and is represented by a switch handle, which may be turned to alternate on and off positions.

The manner `in which this first embodiment of the invention serves its purpose may be readily understood from the foregoing description. As the tow target 10 is being reeled in by winding rotation of the reel 18 and the tow target approaches the towing aircraft, the operator makes sure that the override switch 76 is closed and simply adjusts the potentiometer 75 in accord with the reading of the tachometer 78. When the tow target enters the conical sea-t 54 to retract the launcher tube 35, the largemesponsive switch 66 immediately closes to energize the brake and the brake exerts braking force in accord with the setting of the potentiometer 75. All but residual momentum of small magnitude of the rotating reel is absorbed by the time the tow target completely retracts the launcher tube 35. The complete retraction of the launcher tube 35 results in latching of launcher tube by the latching pawl 50 with the tow target latched to the retracted launcher tube. The brake 24 may then be released by opening the override switch 76, if desired, since the tow target is held in its snubbed position independently of the towline 12.

In the second practice of the invention illustrated by FIG. 8, the brake 24 is controlled by the output of an amplifier 84 which is connected by leads 85 to a suitable voltage source. The amplifier S4 is connected to the brake 24 by a pair of conductors 86 and 8S through the two previously mentioned switches 66 and 76 in series. The input side of the amplifier is connected by conductors 90 and 92 to the output of a tachometer generator 914 that is operated by the reel 18. A sw-itch 95 may be inserted between the tachometer generator and the amplifier. In this practice of the invention, the potentiometer 7S is, of course, omitted.

In employing the brake control arrangement illustrated in FIG. 8, the operator merely makes sure that the override switch 76 and the tachometer generator switch 95 are closed as the tow target approaches the towing aircraft in the operation of reeling in the tow target. The signal transmitted to the input of the amplifier 84 by the tachometer generator 94 determines the amount of current that the amplifier supplies to the brake 2.4 and thereby determines the amount of braking force exerted by the brake. Thus the brake 24 is automatically adjusted with respect to -its braking force in accord with the instant speed of rotation of the reel 18. When the switch 66 in FIG. 8 is closed by the arrival of the tow target at the launcher, the brake is thereby applied for substantially complete deceleration of' the reel 1S by the time the launcher is completely retracted. The launcher tube is automatically latched and the tow target is automatically latched to the launcher as heretofore described. As soon as the reel stops rotating, the tachometer generator ceases to function and the brake 24 is released, the tow target remaining locked to the retracted launcher tube 35.

In the third practice of the invention illustrated by FIG. 9, the tachometer generator 94 is connected to the input of an amplifier 96 in the previously described manner through a pair of conductors 97 and 9S and a switch 99. The amplifier 96, which is energized by a suitable source, is operatively connected to a function generator as indicated by the broken line 104i. In this instance, the function generator comprises a card potentiometer 101 with a wiper 102 that is movable by the amplifier 96. One lead 103 from an source is connected to the card potentiometer 101 and a second lead 104 is connected to the brake. The wiper 102 is connected to the brake through the previously mentioned target-responsive switch 66 and override switch 76.

This third practice of the invention illustrated by FIG. 9 functions in a manner similar to the practice of the invention illustrated by FIG. 8. As the tow target approaches the towing aircraft in the operation of retrieving the tow target, the operator makes sure that the switches 99 and 76 are closed. The amplifier 96 regulates the position of the wiper 102 in accord with the instant rate of rotation of the reel and thus regulates the force that the brake 24 applies when the target-responsive switch 66 is closed. The advantage fof providing the function generator or `card potentiometer is that it makes it possible to make the braking `force vary in any desired manner in response to changes in speed of rotation of the reel. Thus the card potentiometer may compensate for friction involved in the rotation of the reel and may compensate for the time required for current to build up and subsequently decay in the brake circuit.

My description in specific detail of the selected practices of the invention Iwill suggest various changes, substitutions and other departures from my disclosure within the spirit and scope of the appended claims.

I claim:

l. In an apparatus on an aircraft for retrieving a tow target on la towline wherein a power actuated reel on the aircraft equipped with a brake winds -in the towline at various rates to pull the tow target against a movable seat on the aircraft to retract the seat through a given range `against the resistance of a spring, the combination therewith o-f means to actuate the brake in response to entry of the tow target into said seat and means to control the force the brake applies in accordance with the speed Yof the reel to stop the retraction `of the seat within said range.

2. An apparatus as set forth in claim 1 in which said responsive means comprises a switch in a brake control circuit, said switch being responsive to initial retraction of the seat.

3. In an apparatus on an aircraft for retrieving a tow target on a towline wherein a power actuated reel on the aircraft equipped with an electrically actuated brake winds in the towline -to pull the tow target against a movable seat on the aircraft to retract the seat through a given range against the resistance of a spring, the combination therewith of: an source to actuate the brake; .manually operable means to adjust -the braking force applied by the brake in accordance with lthe speed of the reel to stop the retraction of the seat within said range; and a normally open switch to connect the brake with said source, said switch closing in yresponse to arrival of the tow target at said seat.

4. An apparatus as set forth in claim 3 which includes a second normally closed manually `operable switch for releasing said brake when said seat is retracted.

5. In an apparatus `on an aircraft for retrieving a tow target on a towline wherein a power `act-uated reel on the aircraft equipped with an electrically actuated brake winds in the towline to pull the tow target against a movable seat on the aircraft to retract the seat through a given range against the resistance of a spring, the combination therewith of: an source -to actuate the brake; manually operable means to adjust the braking force applied by the brake to stop the retraction of the seat within said range; a tachometer operated by said reel for guidance in adjusting the braking force applied by said brake; and 4a nonmally open switch to close for operating the brake, said switch being responsive to arrival of the tow target at said seat.

6. An apparatus as set forth in claim 5 in which said switch is responsive to the initial retraction of the seat by the tow target.

7. An apparatus as set forth in claim 5 in which said manually operable means is a variable resistor calibrated in terms of the scale of the tachometer.

8. In lan apparatus on an aircraft for retrieving a tow target `on a towline wherein a power actuated reel on the aircraft equipped with an electrically actuated brake winds in the towline to pull the tow target against a mov- -able seat on the aircraft to retract the seat through a given range against the resistance of a spring, the combination therewith of means responsive to rotation of said reel to -generate a signal varying in value in accordance with the rate `of rotation lof the reel; means responsive to said signal generating means to vary the braking force exerted by said brake in accordance with the value of the signal; and means to operate said brake in response to the arrival of the tow `target at said seat.

9. An apparatus as set forth in claim 8 which includes a second means to `disconnect the -means to operate the brake to release the brake when the reel is not rotating.

10. In an apparatus on an aircraft for retrieving a tow target on a towline wherein a power actuated reel on the aircraft equipped with an electro-responsive brake winds in the towline to Ipull the tow target against a movable seat on the aircraft to retract the seat against the resistance of a spring, the combination therewith of: a tachometer generator operatively connected to the reel to generate current varying in value with the rate of rotation of the reel; an amplifier; circuitry connecting said generator with the input of said amplifier and operatively connecting said amplifier with said electro-responsive brake for control of the braking force in accord with the rate of rotation of the reel; and a switch in said circuitry to make the circuitry operative for actuating the electro-responsive brake in response to arrival of the aerial object at said seat.

11. An apparatus as set forth in claim 10 'which includes rneans for releasing said brake when the reel is not rotating.

12. An apparatus as set forth in claim 10 in which said switch is responsive to initial `retraction of the seat by the aerial object.

13. In an apparatus on an aircraft for retrieving a tow target on a towline wherein a power actuated reel on an aircraft equipped with an electrically actuated magnetic brake winds in the towline to pull the aerial object against a movable seat on the aircraft to retract the seat against the resistance of a spring, the combination therewith of: a tachometer generator operatively connected to the reel to generate current varying in value with the rate of rotation of the reel; a circuit to energize said electrically actuated magnetic brake; means in said circuit movable to vary the current supplied to the electrically actuated magnetic brake; an amplier having its input connected to said generator, said amplier controlling said movable means to vary the braking force in accord with the rate of rotation of the reel; and means to close said circuit in response to arrival of lthe tow target at said seat.

References Cited in the tile of this patent UNITED STATES PATENTS 1,309,377 Underhill July 8, 1919 2,040,660 Lenhart May 12, 1936 y2,187,575 Schroeder Jan. 16, 1940 2,272,213 Lear Feb. 10, 1942 2,751,167 Hopper et al. June 19, 1956 2,757,878 Troendle Aug. 7, 1956 2,848,179 TroXell et al Aug. 19, 1958 FOREIGN PATENTS 61,725 Norway Nov. 20, 1939 

1. IN AN APPARATUS ON AN AIRCRAFT FOR RETRIEVING A TOW TARGET ON A TOWLINE WHEREIN A POWER ACTUATED REEL ON THE AIRCRAFT EQUIPPED WITH A BRAKE WINDS IN THE TOWLINE AT VARIOUS RATES TO PULL THE TOW TARGET AGAINST A MOVABLE SEAT ON THE AIRCRAFT TO RETRACT THE SEAT THROUGH A GIVEN RANGE AGAINST THE RESISTANCE OF A SPRING, THE COMBINATION THEREWITH OF MEANS TO ACTUATE THE BRAKE IN RESPONSE TO ENTRY OF THE TOW TARGET INTO SAID SEAT AND MEANS TO CONTROL THE FORCE THE BRAKE APPLIES IN ACCORDANCE WITH THE SPEED OF THE REEL TO STOP THE RETRACTION OF THE SEAT WITHIN SAID RANGE. 